transition_graph {pomdp}

Transition Graph

Description

Returns the transition model as an igraph object.

Usage

transition_graph(
  x,
  action = NULL,
  episode = NULL,
  epoch = NULL,
  state_col = NULL,
  simplify_transitions = TRUE,
  remove_unavailable_actions = TRUE
)

plot_transition_graph(
  x,
  action = NULL,
  episode = NULL,
  epoch = NULL,
  state_col = NULL,
  simplify_transitions = TRUE,
  main = NULL,
  ...
)

Arguments

x

object of class POMDP or MDP.

action

the name or id of an action or a set of actions. Bey default the transition model for all actions is returned.

episode, epoch

Episode or epoch used for time-dependent POMDPs. Epochs are internally converted to the episode using the model horizon.

state_col

colors used to represent the states.

simplify_transitions

logical; combine parallel transition arcs into a single arc.

remove_unavailable_actions

logical; don't show arrows for unavailable actions.

main

a main title for the plot.

...

further arguments are passed on to igraph::plot.igraph().

Details

The transition model of a POMDP/MDP is a Markov Chain. This function extracts the transition model as an igraph object.

Value

returns the transition model as an igraph object.

See Also

Other POMDP: MDP2POMDP, POMDP(), accessors, actions(), add_policy(), plot_belief_space(), projection(), reachable_and_absorbing, regret(), sample_belief_space(), simulate_POMDP(), solve_POMDP(), solve_SARSOP(), update_belief(), value_function(), write_POMDP()

Other MDP: MDP(), MDP2POMDP, MDP_policy_functions, accessors, actions(), add_policy(), gridworld, reachable_and_absorbing, regret(), simulate_MDP(), solve_MDP(), value_function()

Examples

data("Tiger")

g <- transition_graph(Tiger)
g

plot_transition_graph(Tiger)
plot_transition_graph(Tiger, vertex.size = 20, 
                      edge.label.cex = .5, edge.arrow.size = .5, margin = .5)
plot_transition_graph(Tiger, vertex.size = 60, 
                      edge.label = NA, edge.arrow.size = .5, 
                      layout = rbind(c(-1,0), c(+1,0)), rescale = FALSE)

## Plot an individual graph for each actions and use a manual layout.
for (a in Tiger$actions) {
 plot_transition_graph(Tiger, action = a, 
                        layout = rbind(c(-1,0), c(+1,0)), rescale = FALSE,
                        main = paste("action:", a))
}

## Plot using the igraph library
library(igraph)
plot(g)

# plot with a fixed layout and curved edges
plot(g,
 layout = rbind(c(-1, 0), c(1, 0)), rescale = FALSE,
 edge.curved = curve_multiple_directed(g, .8),
 edge.loop.angle = -pi / 4,
 vertex.size = 60
 )

## Use visNetwork (if installed)
if(require(visNetwork)) {

g_vn <- toVisNetworkData(g)
nodes <- g_vn$nodes
edges <- g_vn$edges

# add manual layout
nodes$x <- c(-1, 1) * 200
nodes$y <- 0

visNetwork(nodes, edges)  %>%
  visNodes(physics = FALSE) %>%
  visEdges(smooth = list(type = "curvedCW", roundness = .6), arrows = "to")
}